When running this code:

    public async Task<IActionResult> AddMessage()
    {
        int distid = ViewBag.DISTRIBUTORID;
        ViewBag.PageName = "Send Message";

        int id = Convert.ToByte(ViewBag.ID);
        ViewBag.UserId = id;

        var messages = await _companyContext.MESAJLAR.Where(p => p.SENDERID == id || p.SENTID == id).OrderBy(p => p.DATE).GroupBy(p => p.SPECIALID).Select(p => p.Last()).ToListAsync();
        var ids1 = messages.Select(p => p.SENDERID).ToArray();
        var ids2 = messages.Select(p => p.SENTID ).ToArray();

        var users= await _userDatabaseContext.user.Where(p => p.DISTID == distid && p.ID != id && !ids1.Contains(p.ID) && !ids2.Contains(p.ID)).ToListAsync();

        return View(new AddMessageViewModel
        {
            USERS= users
        });
    }

I get the following error:

Queries performing 'Last' operation must have a deterministic sort order.Rewrite the query to apply an 'OrderBy' operation on the sequence before calling 'Last'.

I'm getting it at the line that starts with var messages = ...

CodePudding user response：

The Problem with your query is, that you are trying to select .Last() without ordering your data first. Right now you are ordering your data, then group it and after that you try to select 'Last()'. You have to order the grouped data to use '.Last()'.

var messages = await _companyContext.MESAJLAR.Where(p => p.SENDERID == id || p.SENTID == id).OrderBy(p => p.DATE).GroupBy(p => p.SPECIALID).OrderBy(p => p.XXXXX).Select(p => p.Last()).ToListAsync();

And your first order would probably be not needed anymore.